Thursday, September 3, 2009

Updates on Climate Change

The Toronto Star runs the expected piece, on the verge of the Copenhagen conference, saying Arctic ice is definitely retreating, this is definitely a sign of global warming, etc. No reference to the fact that in 2007, it may have been more the case that the ice was moved by wind and ocean currents to a warmer place, where it melted, than that it melted in its usual cold place.

I'll just note these sentences:

"Evidence for responses of atmospheric circulation to declining sea ice extent is just beginning to emerge," the report says.

Sea water once covered by ice becomes warmed by the sun, changing ocean currents that begin in the Arctic. Those currents are also affected by meltwater flooding into the oceans, altering its salinity.

Ocean currents - major climate determinants in coastal regions - have yet to show significant climate-change impacts, but scientists are growing more concerned about the possibility.

Then, upping the ante: "Arctic is the warmest it's been in 2,000 years."

The new report is based on a decade-by-decade reconstruction of temperatures over the past 2,000 years developed using information from ancient lake sediments, ice cores, tree rings and other samples. The findings were then compared with complex computer climate model simulations created at the National Center for Atmospheric Research in Boulder, Colorado.

Moving away from the Arctic, there is new evidence that the Indo-Pacific warm pool was as warm in the Medieval Warm Period as it is today. Delia Oppo, a paleo–oceanographer with the Woods Hole Oceanographic Institution says:

“The more interesting and potentially controversial result is that our data indicate surface water temperatures during a part of the Medieval Warm Period that are similar to today’s,” says Oppo. NH temperature reconstructions also suggest that temperatures warmed during this time period between A.D. 1000 and A.D. 1250, but they were not as warm as modern temperatures. Oppo emphasizes, “Our results for this time period are really in stark contrast to the Northern Hemisphere reconstructions.”

That is, the new findings contradict the Northern Hemisphere or NH findings, the basis of the Mann "hockey stick" and similar summaries indicating that the twentieth century was the warmest in some time. The Medieval period presumably had little influence from man-made emissions. Oppo and colleagues sound like cautious scientists, and there are caveats here:

Oppo cautions that the reconstruction contains some uncertainties. Information from three different cores was compiled in order to reconstruct a 2,000-year-long record. In addition sediment data have an inherent uncertainty associated with accurately dating samples. The SST variations they have reconstructed are very small, near the limit of the Mg/Ca dating method.

Jonah Goldberg has written a nice piece,showing a bit more caution than I sometimes do.

Meanwhile, the journal Science reports that a study led by the National Center for Atmospheric Research, or NCAR, has finally figured out why increased sunspots have a dramatic effect on the weather, increasing temperatures more than the increase in solar energy should explain. Apparently, sunspots heat the stratosphere, which in turn amplifies the warming of the climate.

Scientists have known for centuries that sunspots affect the climate; they just never understood how. Now, allegedly, the mystery has been solved.

Last month, in another study, also released in Science, Oregon State University researchers claimed to settle the debate over what caused and ended the last Ice Age. Increased solar radiation coming from slight changes in the Earth’s rotation, not greenhouse-gas levels, were to blame.

Goldberg doesn't rush to the conclusion that the alarmists are wrong, and the skeptics are right. He simply says there is some reason for skepticism: natural causes, especially originating from the sun, may have more influence than the alarmists admit, and man-made causes may have less.

What does it say that the modeling that guaranteed disastrous increases in global temperatures never predicted the halt in planetary warming since the late 1990s? (MIT’s Richard Lindzen says that “there has been no warming since 1997 and no statistically significant warming since 1995.”) What does it say that the modelers have only just now discovered how sunspots make the Earth warmer?

I don’t know what it tells you, but it tells me that maybe we should study a bit more before we spend billions to “solve” a problem we don’t understand so well.

Of course, the scientists whose work raises questions about alarmism, when they are quoted, still say: this is not solid evidence against global warming/climate change, etc. That often seems like singing the same hymn at the end of every church service.

UPDATE Sept. 4:

Anthony Watts has a pretty thoughtful beginning to a discussion of the new Arctic findings. There is still not much data about the Arctic as a whole, and there is a tendency to be selective as to which data is chosen.

Still, these Arctic findings look like about the best data so far indicating warming precisely in the twentieth century. Maybe not exactly the whole century, or the right parts, but ...